Piezoelectric crystal holder



April 6,` 1937.

R. BECHMANN 5T A1. 2,076,060

PIEZOELEGTRIC CRYSTAL HOLDER Filed oct. 12', 19:55'

WlLHELM SCHNEIDER ATTORNEY.

Patented Apr. 6, 1937 PATENT OFFICE PIEZOELECTRIC Y rCRYSTAL HOLDERRudolf Bechmann and Wilhelm Schneider, Berlin,

Germany, assignors to Telefunken Gesellschaft fr Drahtlose Telegraphiem. b. H., Berlin, Germany, a corporation of Germanyk ApplicationOctober, 12, 1935, Serial No. 44,674 In Germany November 6, 1934 9Claims.

This invention relates to a new and novel hold-v er for a piezo-electriccrystal oscillator.

This application is a continuation in part of application Serial No.738,454, iiledr August 4,`

In the above-mentioned patent application, ay

holder or setting means for oscillators of the piezo-electric crystaltype has been disclosed, the

essential feature of which is that the crystal andA l0 the electrodesare embedded inside a casing consistingA of ceramic material.

lowing considerations.` o

'The temperature coefficient of a vcrystal device consists of thetemperature coefficient of the crys-;

selfA by choosing a suitable cut. .Hence still further decrease of thetemperature coeflicient of'.

the entire device is obtainable only by a reduction of the temperaturecoeflicient of the crystal holder. yEspecially in the case of holders ofsuch crystal oscillators as are called upon to insure an extremelyhigh-frequency stability or constancy, for instance, when employed ascrystal monitors in connection with transmitters or as quartz clocks, itis of essential importance that the temperature coeflicient be keptsmall.

As a general rule, the electrodes are at an extremely small distancefrom the surfaces of the crystal; but this interval of space andl itsstability or preservation is essential from the Viewpoint of theoscillatory state and the frequency stability of the crystal. As aresult, even changes in the distance should be avoided which, per se,would be small, but which would exercise a high percentage influence. Infact, it has been for this reason that the earlier filed patentapplication contains the instruction that the electrodes should beconfined inside a casing consisting of ceramic material, the underlyingidea being to utilize the small temperature coeicient of ceramics ratherthan the higher temperature coefficient of metal.

Now, according to this invention, not only for the casing, but also fora portion of the principal mass of the electrodes, ceramic material isemployed, such necessary metallic surface portions of the electrodes asare placed opposite the crystal being, if desired, metallized for thepurpose of obtaining electric conductivity. In order to preclude soilingof the electrode surfaces by atmos- The present invenf tion discloses afurther improvement of the said crystal holder which is predicated uponthe :fol-

pheric agencies, for these are liable to cause irregularities of thesurface and partial changes in the interelectrode distance, itisrecommendable to use for metallization the surface with a kind of metal,preferably chromium, that will bc stable both in reference toatmospheric and humidity actions, I

One exemplified embodiment of the invention is illustrated in thedrawing in which Fig. 1 shows `a plan view of the crystal holder, aportion 0f- Which is broken away to showk the inner construction; Fig. 2is a cross section ofFig. l; Fig. 3 is an enlargeddetailed portion ofFig. 2. The ringlike casing made kof ceramic material l, surrounds theoscillator crystal 2 which is planar or laminar in form, and which issecured by centering ring 3. SupportingA of the crystal is effected inthis manner that the crystal plate has `a peripheral groove or slot intowhich engage v yieldingly or elastically the peaks or supporting studs 3inserted in the centering ring 3. The latter is clamped fast on bothsides by insulating ringsA made of ceramic material 4, and the electrodeholder means 5; These latter, as shown in f the drawing, are securedonthe casing I by means of a screw threadedjoint. The electrodes desig`nated Iby 6 are of ceramic material and they are metallized upon theworking or` active surfaces 6 whichare located opposite `the crystal Toinsure adjustment of the distance between the electrode surfaces and thecrystal, the electrode bodies 6 are embedded in metal rings or caps 1which have a fine-pitched male screw thread 1', by means of which theyare adjustable in the bushing-like electrode holders 5 which have femalethread. In order to x the distance once adjusted, there is provided thescrew-threaded rings 8 arranged on both sides. The ceramic casing capsor cover pieces l0 on both sides are united with the casing l by meansof screws l2.

The preferable plan is to make the casing fasten ing screws I2, asshown, in such a Way that one and the same bolt serves to secure, on theone hand, the electrode holder 5, and, on the other hand, the casing capI0.

For the purpose of establishing conductive connection with the electrodemetallized surfaces, there is provided a metallic spindle 9 which isfixed within the electrode body 6 and in conductive connection with theelectrode rnetallized sur" faces, said spindle 9 being maintained inelectrical contact with a lead-in supported in cap I0. In order toinsure safe contact-making, lead Il is made yielding such that itsspindle stud i I is pressed against the end surface of conductor B byvirtue of spring I3 applying pressure to member 9.

Having thus described our invention, what we claim is:

l. A piezo-electric Crystal holder comprising an insulating casing, acrystal within said casing, a supporting member for said crystal, twoinsulating members located at each side of said crystal, said insulatingmembers having their Surfaces that face said crystal lcoated with metalto act as an electrode for said crystal.

2. A piezo-electric crystal holder comprising an insulating casing ofceramic material, a crystal within said casing, a supporting member forsaid crystal, two insulating members of ceramic material located at eachside of said crystal, said insulating members having their surfaces thatface said crystal coated with metal to act as an electrode for saidcrystal.

3. A piezo-electric crystal holder comprising an insulating casing, acrystal within said casing, a supporting member for said crystal, twoadjustable insulating members located at each side of said crystal, saidinsulating members having their surfaces that face said crystal coatedwith metal to act as an electrode for said crystal, and means forconnecting said metal surfaces outside of said casing.

4. A piezo-electric crystal holder comprising a ring-like insulatingcasing having removable end caps, a crystal within said casing, asupporting member for said Crystal, two insulating members located ateach side of said crystal, said insulating members having their surfacesthat face said crystal coated with metal to act as an electrode for saidcrystal.

5. A piezo-electric crystal holder comprising an insulating casinghaving removable end caps, a crystal within said casing, a ring-likesupporting member for supporting and surrounding said crystal, securingmeans whereby said supporting member is secured within said casing, twoinsulating members located each side of said crystal, said insulatingmembers having their surfaces that face said crystal coated with metal,each of said metal surfaces acting as an electrode for said crystal.

6. A piezo-electric crystal holder comprising an insulating 'casinghaving removable end caps, a

crystal within said casing, a ring-like supporting member for supportingand surrounding said crystal, securing means whereby said supportingmember is secured within said casing, two adjustable insulating memberslocated each side of said crystal, said insulating members having theirsurfaces that face said crystal coated with metal, each of said metalsurfaces acting as an electrode for said crystal.

7. A piezo-electric crystal holder comprising an insulating casinghaving removable end caps, a crystal within said casing, a ring-likesupporting member for supporting and surrounding said crystal, securingmeans whereby said supporting member is secured within said casing, twoinsulating members located each side of said crystal, said insulatingmembers having their surfaces that face said crystal coated with metal,each of said metal surfaces acting as an electrode for said crystal, andmeans passing through the end of said Casing for connecting saidmetallic surfaces outside of said casing.

8. A piezo-electric crystal holder comprising an insulating casinghaving removable end caps, a crystal within said casing, a ring-likesupporting member for supporting and surrounding said crystal, securingmeans whereby said supporting member is secured within said casing, twoinsulating members located each side of said crystal, said insulatingmembers having their surfaces that face said crystal coated with metal,each of Said metal surfaces acting as an electrode for said crystal, andmeans passing through the central portion of said insulating members andthrough the end of said casing for connecting said metal surfacesoutside of said casing.

9. A piezo-electric crystal holder comprising an insulating casinghaving removable end caps, a crystal within said casing, a supportingmember surrounding said crystal, securing means whereby said supportingmember is secured within said casing, two insulating members havingthreaded bushings secured to each end thereof for adjusting said memberswith respect to said crystal, said insulating members having theirsurfaces that face said crystal coated with a metal to act as anelectrode for said crystal.

RUDOLF BECHMANN. WILHELM SCHNEIDER.

